The long COVID syndrome: A conundrum for the allergist/immunologist

Understanding the mechanisms and treatments of long COVID to address future public health risks

The 2019 coronavirus disease (COVID-19), triggered by the severe acute respiratory syndrome coronavirus (SARS-CoV-2), has seen numerous individuals undergo and recover from it, drawing extensive attention to their health conditions. Extensive studies indicate that even after surpassing the acute phase of infection, patients continue to experience persistent symptoms such as fatigue, pain, depression, weakening, and anosmia. COVID-19 appears not to have concluded but rather to persist long-term in certain individuals, termed as "long COVID." This represents a heterogeneous ailment involving multiple organ systems, with a perceived complex and still elusive pathogenesis. Among patients with long COVID, observations reveal immune dysregulation, coagulation impairments, and microbial dysbiosis, considered potential mechanisms explaining sustained adverse outcomes post COVID-19. Based on the multifactorial nature, varied symptoms, and heterogeneity of long COVID, we have summarized several categories of current therapeutic approaches. Furthermore, the symptoms of long COVID resemble those of other viral illnesses, suggesting that existing knowledge may offer novel insights into long-term COVID implications. Here, we provide an overview of existing literature associated with long COVID and summarize potential mechanisms, treatment modalities, and other analogous conditions. Lastly, we underscore the inadequacies in long COVID treatment approaches and emphasize the significance of conducting further research and clinical trials.

Different polarization and functionality of CD4+ T helper subsets in people with post-COVID condition

Introduction

After mild COVID-19 that does not require hospitalization, some individuals develop persistent symptoms that may worsen over time, producing a multisystemic condition termed Post-COVID condition (PCC). Among other disorders, PCC is characterized by persistent changes in the immune system that may not be solved several months after COVID-19 diagnosis.

Methods

People with PCC were recruited to determine the distribution and functionality of CD4+ T helper (Th) subsets in comparison with individuals with mild, severe, and critical presentations of acute COVID-19 to evaluate their contribution as risk or protective factors for PCC.

Results

People with PCC showed low levels of Th1 cells, similar to individuals with severe and critical COVID-19, although these cells presented a higher capacity to express IFNγ in response to stimulation. Th2/Th1 correlation was negative in individuals with acute forms of COVID-19, but there was no significant Th2/Th1 correlation in people with PCC. Th2 cells from people with PCC presented high capacity to express IL-4 and IL-13, which are related to low ventilation and death associated with COVID-19. Levels of proinflammatory Th9 and Th17 subsets were significantly higher in people with PCC in comparison with acute COVID-19, being Th1/Th9 correlation negative in these individuals, which probably contributed to a more pro-inflammatory than antiviral scenario. Th17 cells from approximately 50% of individuals with PCC had no capacity to express IL-17A and IL-22, similar to individuals with critical COVID-19, which would prevent clearing extracellular pathogens. Th2/Th17 correlation was positive in people with PCC, which in the absence of negative Th1/Th2 correlation could also contribute to the proinflammatory state. Finally, Th22 cells from most individuals with PCC had no capacity to express IL-13 or IL-22, which could increase tendency to reinfections due to impaired epithelial regeneration.

Discussion

People with PCC showed skewed polarization of CD4+ Th subsets with altered functionality that was more similar to individuals with severe and critical presentations of acute COVID-19 than to people who fully recovered from mild disease. New strategies aimed at reprogramming the immune response and redirecting CD4+ Th cell polarization may be necessary to reduce the proinflammatory environment characteristic of PCC.

The Long Road of Long COVID: Specific Considerations for the Allergist/Immunologist

Long COVID (coronavirus disease 2019) syndrome, also known as post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, is a new disorder that can develop after an acute infection with the SARS-CoV-2 virus. The condition is characterized by multiorgan system involvement with a wide range of symptoms that can vary in severity from mild to debilitating. Some of the common symptoms associated with long COVID syndrome include cardiovascular issues such as heart palpitations and chest pain; thrombotic events (eg, blood clotting disorders); metabolic problems (eg, type 2 diabetes); dysautonomia; paroxysmal orthostatic tachycardia syndrome; myalgic encephalomyelitis/chronic fatigue syndrome; reactivation of the Epstein-Barr virus; the presence of autoantibodies; chronic spontaneous urticaria (hives); and connective tissue diseases. Whereas long COVID syndrome can affect individuals from various backgrounds, certain populations may be at higher risk such as individuals of Hispanic and Latino heritage, as well as those with low socioeconomic status, although approximately one-third of affected patients have no known risk factors or preexisting conditions. Many survivors of COVID-19 struggle with multiple symptoms, increased disability, reduced function, and poor quality of life. Whereas vaccination has been the most significant intervention able to decrease the severity of acute SARS-Cov2 infection and curtail deaths, limited data are available related to its modulating effect on long COVID necessitating the need for further investigation. Furthermore, several inflammatory pathways have been proposed for the pathogenesis of long COVID that are the targets for ongoing clinical studies evaluating novel pharmacological agents. The purpose of the present report is to review the many factors associated with long COVID with a focus on those aspects that have relevance to the allergist-immunologist.

Symptom flares after COVID-19 infection versus vaccination among youth with PANS/PANDAS

Background: Flares of autoimmune conditions can happen after coronavirus disease 2019 (COVID-19) infection and after COVID-19 vaccines. Patients and clinicians confront difficult decisions about vaccine safety when considering efforts to balance the risks of disease exacerbation after vaccines versus the protection that vaccines offer to potential serious life-threatening complications of COVID-19 infection. Objective: To examine symptom flares after COVID-19 infection and vaccines in the case of a form of autoimmune encephalitis that primarily affects children and young adults (pediatric acute-onset neuropsychiatric syndrome [PANS] / pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections [PANDAS]). Method: A cross-sectional study that used a survey distributed through PANS/PANDAS groups, organizations, and clinics. Results: Surveys were completed by 496 parents and/or caregivers of children with PANS/PANDAS. Among the children reported to have had a COVID-19 infection (n = 178), 43% reported severe flares of PANS/PANDAS symptoms, 23% reported mild flares, and 30% reported no symptom flares. Among those who had received COVID-19 vaccines (n = 181), 65% observed no changes in PANS/PANDAS symptoms after the vaccine, 19% reported mild flares, and 15% reported severe flares. Paired sample t-tests showed that, after COVID-19 infections, children with PANS/PANDAS were significantly more likely to experience a severe symptom flare than a mild flare or no change in symptoms. In contrast, after receiving COVID-19 vaccines, children were significantly more likely to experience no change in PANS/PANDAS symptoms than to endure a mild or severe symptom flare. In addition, children who recovered from PANS/PANDAS were significantly more likely to have no symptom change versus children who were managing the condition, both after COVID-19 infection (92% versus 25%) and vaccine receipt (100% versus 66%). Conclusion: These results support COVID-19 vaccination for most individuals with PANS/PANDAS given that the frequencies of symptom flares and setbacks after COVID-19 infection were significantly higher than after the COVID-19 vaccine. Nonetheless, further studies are needed to fully assess the risk-benefit balance and to provide a more individualized approach to disease prevention in people with immune vulnerabilities.

Cellular miR-6741-5p as a Prognostic Biomarker Predicting Length of Hospital Stay among COVID-19 Patients

Wide variability exists with host response to SARS-CoV-2 infection among individuals. Circulatory micro RNAs (miRNAs) are being recognized as promising biomarkers for complex traits, including viral pathogenesis. We hypothesized that circulatory miRNAs at 48 h post hospitalization may predict the length of stay (LOS) and prognosis of COVID-19 patients. Plasma miRNA levels were compared between three groups: (i) healthy volunteers (C); (ii) COVID-19 patients treated with remdesivir (an antiviral) plus dexamethasone (a glucocorticoid) (with or without baricitinib, a Janus kinase inhibitor) on the day of hospitalization (I); and COVID-19 patients at 48 h post treatment (T). Results showed that circulatory miR-6741-5p expression levels were significantly different between groups C and I (p < 0.0000001); I and T (p < 0.0000001); and C and T (p = 0.001). Our ANOVA model estimated that all patients with less than 12.42 Log2 CPM had a short LOS, or a good prognosis, whereas all patients with over 12.42 Log2 CPM had a long LOS, or a poor prognosis. In sum, we show that circulatory miR-6741-5p may serve as a prognostic biomarker effectively predicting mortality risk and LOS of hospitalized COVID-19 patients.